Possible Clues:

• 27 across gets rot and that's flat
• Large food fish
• Fish served up almost too dry
• Motor's given its heart to fish
• Bouillabaisse fish
• B in a trout to be another fish, and that's flat
• Fish is almost too dry when served up
• Fish hung up to dry
• Species of flatfish
• Be a little in a trout for another fish